1. Field of Invention
This invention pertains to a support for shades, including cellular shades and other window treatments, and more particularly, to a mechanism with an improved and more effective head rail and clutch.
2. Background of the Invention
In recent years, a number of mono-control mechanisms were invented that allow lifting and lowering of cellular blinds. The early mechanisms were developed that utilized clutches and rotating lift, which required substantially more space than traditional cord, lock devices. The height and depth of these mechanisms usually exceeded 1 inch. Moreover, typically the drop length of the shade would determine the size of the spool in which lifting tape would be gathered. The longer the drop, the bigger the spool and head rail had to be. In other words, due to the complexity of the clutch mechanisms and the lift sets utilizing cords and tapes, larger head rails had to be developed to provide proper enclosure for these mechanisms. The size, and more particularly weight of the fabric of the shade were the major factors for the requirement of big clutch mechanisms. However, oversized head rail enclosures were objectionable because they detracted from the esthetical appearance of the shade.
Another disadvantage of the early mechanisms pertained to the structure of the pulley in the clutch. Typically the perimeter of the pulley was designed with series of rigid ramps with sharp edges forming a serpentine path receiving and engaging a cord trained around the perimeter. Sharper and more aggressive edges provided a solid engagement with the cord, thereby increasing the friction between the cord and the pulley and decreasing, or even eliminating slippage. By the same token, however, these sharp edges also tended to cut and fray the cord fibers and therefore reduce the useful life of the cord.